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β-delayed proton decays near the proton drip line

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Science china(physics,Mechanics & Astronomy) 2005年第3期48卷 257-267页

作者： XU Shuwei 1 , LI Zhankui 1 , XIE Yuanxiang 1 , HUANG Wenxue 1 , SHU Nengchuan 2., CHEN Yongshou 2., XU Furong 3 , WANG Kun 4., PAN Qiangyan 1 , WANG Xudong 1 , YU Yong 1 & XING Yebing 1 1. Institute of Modern physics, Chinese Academy of Sciences, Lanzhou 730000, china 2. Nuclear physics department, china Institute of Atomic Energy, Beijing 102.13, china 3. department of Technical physics, Peking University, Beijing 100871, china 4. Shanghai Institute for Nuclear Research, Shanghai 2.1800, china Institute of Modern physics Chinese Academy of Sciences Lanzhou China Nuclear physics department China Institute of Atomic Energy Beijing China department of Technical physics Peking University Beijing China Shanghai Institute for Nuclear Research Shanghai China

We briefly reviewed the experimental study on a-delayed proton decays near the proton drip line published by our group during the period of 1996―2.04. namely the first observation of the a-delayed proton decays of 9 new nuclides in the rare-earth region and the new measurements of a-delayed proton decays of 5 nuclides in the mass ～90 region near the N = Z line with the aid of the “p-?” coincidence in combination with a He-jet tape transport system. In the meantime some important experimental technique details were supplemented. The experimental results, including the half -lives, spins, parities, deformations and production reaction cross sections for the 14.nuclei were summarized and compared with the current nuclear-model predictions, and then the following points were represented. (1) The experimental half-lives for 85Mo and 92.h as well as the predicted “waiting point” nuclei 89Ru and 93Pd are 5―10 times longer than the theoretical predictions given by M?ller et al. using a macroscopic-microscopic model. It considerably influences the predictions of the abundances of the nuclides produced in the rp-process. (2. The current-model predictions are not consistent with the experimental assignments of the spins and parities for the proton drip-line nuclei 14.0}o and 12.Pm. However, the nuclear potential energy surface (PES) calculated by using a Woods- Saxon-Strutinsky method reproduced the experimental results. (3) The Alice code overestimated the production reaction cross sections of the studied 9 rare-earth nuclei by one order of magnitude or two, while HIVAP code overestimated them by one order of magnitude approximately.

关键词： proton drip line, β-delayed proton decay, He-jet tape transport system, "p-γ" coincidence, spin, parity, deformation, production reaction cross section.

Effect of an impurity on 3-electron quantum dots in magnetic fields

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Science china(physics,Mechanics & Astronomy) 2004年第5期47卷 521-530页

作者： LIU Yimin1,2. HUANG Gangming1 & BAO Chengguang1 1. department of physics, Zhongshan University, Guangzhou 5102.5,{2. 2. department of physics, Shaoguan University, Shaoguan 512.05,{2. department of physics Zhongshan University Guangzhou China department of physics Shaoguan University Shaoguan China

The ground-state property of a 2.dimensional 3-electron quantum dot (QD) subjected to an external magnetic fieldB and affected by an impurity is studied. The impurity is located at thez-axis by a distanced from the plane of the dot. The evolution of the angular momentumL o and the spinS o of the ground state in accordance withB andd has been calculated, and the results are summarized and plotted in a (L o,S o) diagram. The spatial distribution of the electrons (the size and the geometric features) and the optical absorption have also been investigated. The (L o S o) diagram indicates thatL o andS o may jump whend and/orB vary. It was found that, due to the constraints arising from symmetry, each symmetric geometry is accessible only to a specific group of states having specificL o andS o.

关键词： quantum dot, ground state, charged impurity, magnetic field.

Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of N_(2.molecule

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Science china(physics,Mechanics & Astronomy) 2005年第4期48卷 385-398页

作者： REN Weiyi1,2. SUN Weiguo1, HOU Shilin3 & FENG Hao4.1. Institute of physics, College of Chemical Engineering, Sichuan University, Chengdu 610065, china 2. Institute of Theoretical physics, Xihua Normal University, Nanchong 637002. china 3. {4. of physics, china Oceanography University, Qingdao 2.6003, china 4. College of physics, Sichuan University, Chengdu 610065, china Institute of physics College of Chemical Engineering Sichuan University Chengdu China Institute of Theoretical physics Xihua Normal University Nanchong China department of physics China Oceanography University Qingdao China College of physics Sichuan University Chengdu China

It is usually very difficult to directly obtain molecular dissociation energy De and all accurate high-lying vibrational energies for most diatomic electronic states using modern experimental techniques or quantum theories, and it is also very difficult to give accurate analytical expression for diatomic molecular dissociation energy. This study proposes a new analytical formula for obtaining accurate molecular dissociation energy based on the LeRoy and Bernstein’s energy expression in dissociation limit. A set of full vibrational energy spectra for some electronic states of N2.molecule are studied using the algebraic method (AM) suggested recently, and the corresponding accurate molecular dissociation energies are evaluated using the proposed new formula and high-lying AM vibrational energies. The results show that the AM spectra and the new theoretical dissociation energies agree excellently with experimental data, and thereby providing a new physical approach to generating accurate dissociation energies for electronic states of diatomic molecules.

关键词： vibrational energy, dissociation energy, nitrogen molecule, algebraic method.

Anisotropic effect on the vibronic reduction factors

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Chinese Science Bulletin 2006年第21期51卷 2553-2558页

作者： QIU Qing-chun1,2.& QIAO Fen1,2.1. department of physics and IT, Medical College, Shantou University,Shantou 51504.,{2. 2. department of physics, Shantou University, Shantou 515063,{2. department of physics and IT Medical College Shantou University Shantou China department of physics Shantou University Shantou China

The reduction factors p and q defined by Ham in the Ee JT system and their relation 2.-p=1 have been well accepted and the concept of reduction factors is widely used in the studies of vibronic coupling. However, when the system is under the anisotropic conditions, the reduction factors and their relation will change accordingly. The first-order reduction factors p and q of Ee system were further studied using the method of unitary transformation here. The relation between p and q proposed by Ham was investigated under both conditions of the linear coupling and the anisotropic effects. The result demonstrated that the relation of 2.-p=1 was only correct for the linear vibronic coupling, but not correct when the anisotropic effect was considered. This result suggested that the anisotropic effect influence considerably the reduction factors, and hence the physical properties of materials. Our method could be also applied to other JT systems, especially the highly symmetric JT systems involving C60 molecules.

关键词：电子振动耦合声子交迭 Jahn-Teller效应各向异性

Entropy product measure for multipartite pure states

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Science china(physics,Mechanics & Astronomy) 2006年第5期49卷 606-615页

作者： CAO Wancang1,2. LIU Dan2. PAN Feng3 & LONG Guilu2.4.1. department of {4., Chifeng College, Chifeng 02.001,{2. 2. Key Laboratory for Quantum Information and Measurements, department of {4., Tsinghua University, Beijing 100084.{2. 3. department of {4., Liaoning Normal University, Dalian 11602.,{2. 4. Key Laboratory for Atomic and Molecular Nano-Sciences, Tsinghua University, Beijing 100084.{2. Correspondence should be addressed to Long Guilu department of physics Chifeng College Chifeng China Key Laboratory for Quantum Information and Measurements Department of Physics Tsinghua University Beijing China department of physics Liaoning Normal University Dalian China Key Laboratory for Atomic and Molecular Nano-Sciences Tsinghua University Beijing China

An entanglement measure for multipartite pure states is formulated using the product of the von Neumann entropy of the reduced density matrices of the constituents. Based on this new measure, all possible ways of the maximal entanglement of the triqubit pure states are studied in detail and all types of the maximal entanglement have been compared with the result of ‘the average entropy’. The new measure can be used to calculate the degree of entanglement, and an improvement is given in the area near the zero entropy.

关键词： multipartite pure state von Neumann entropy entanglement measure

Direct CP violation in hadronic B decays

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Science china(physics,Mechanics & Astronomy) 2006年第3期49卷 357-366页

作者： HONG Bihai1,2.& Lü Caidian3 1. department of physics, Lishui University, Lishui 32.000,{2. 2. department of physics, Shanghai Jiaotong University, Shanghai 2.0030, china 3. Institute of High Energy physics, Beijing 10004.,{2. department of physics Lishui University Lishui China department of physics Shanghai Jiaotong University Shanghai China Institute of High Energy physics Beijing China

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on kT factorization, using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

关键词： CP violation hadronic B decay factorization.

Potential energy surfaces for low-lying electronic states of SO_2

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Science china Chemistry 2006年第4期49卷 289-295页

作者： LI Anyang1, SUO Bing2. WEN Zhenyi2.& WANG Yubin2.1. Shanxi Key Laboratory of Physico-inorganic Chemistry, department of Chemistry, Northwest University, Xi’an 710069,{4. 2. Institute of Modern {2., Northwest University, Xi’an 710069,{4. Shanxi Key Laboratory of Physico-inorganic Chemistry Department of Chemistry Northwest University Xi’an China Institute of Modern physics Northwest University Xi’an China

The potential energy surfaces for the nine low-lying electronic states of SO2.have been constructed by using the multi-reference second order perturbation theory (MRPT2. with the basis set cc-pVTZ. The optimized geometries and the adiabatic excitation energies of these states are in good agreement with experiments and previous calculations. The crossings and avoided crossings dis- played in the potential energy surfaces are expounded.

关键词： cross of PES, MRPT2. SO2 (sulfur dioxide).

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

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Science china Chemistry 2004年第2期47卷 106-112页

作者： GONG Yubing1,2. HOU Zhonghuai1 & XIN Houwen1 1. department of Chemical physics, University of Science and Technology of{2., Hefei 2.002.,{2. 2. department of physics, Yantai Teachers University, Yantai 2.4.2.,{2. department of Chemical physics University of Science and Technology of China Hefei China department of physics Yantai Teachers University Yantai China

The dynamical behavior of surface catalytic oxidation reaction of Pt(110)/CO+O2.modulated by colored noise, under the condition of specific temperature, has been investigated when the partial pressure of CO gas is near the supercritical Hopf bifurcation point. By computer simulation the oscillation and stochastic resonance induced by colored noise are observed. The influences of the intensity and correlation time of colored noise on stochastic resonance are discussed. The range of sensitivity of the system to the environmental fluctuation is analyzed.

关键词： colored noise, stochastic resonance, surface catalytic reaction of Pt(110)/CO+O2. supercritical Hopf bifurcation, signal-to-noise ratio (SNR).

Internal noise stochastic resonance in CO oxidation on nm-sized palladium particles

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Science china Chemistry 2005年第5期48卷 395-401页

Based on a stochastic mesoscopic model, the influence of internal noise on the oscillatory kinetics of the catalytic oxidation of CO on nm-sized palladium particles is studied, using the chemical Langevin equations, Poisson approximation algorithm, and exact stochastic simulation algorithm. The reaction rate oscillations are of stochastic nature due to considerable internal noise in such mesoscopic systems. It is found that the performance of the stochastic oscillations undergoes a maximum with the variation of internal noise level for a given CO partial pressure, which demonstrates the occurrence of internal noise stochastic resonance. This phe-nomenon implies that optimal internal noise would favor the reaction rate oscillation of CO oxi-dation on nm particles. Such a phenomenon is robust to the change of external parameters, such as CO pressures.

关键词： nanometer-sized palladium particles, surface catalytic CO oxidation, internal noise, stochastic resonance, chemical Langevin equation.